R-Pro › Field cases › Components

Rotary Discharge Reed Valve Fatigue Failure → High-Side Backflow

Likely causes

Reed valve metal fatigue from accumulated operating cycles

Check: Disassemble compressor; inspect reed valve for cracks, deformation, corrosion — replace discolored (yellow-brown) reeds immediately; use feeler gauge to verify seating, replace if gap > 0.02 mm

What to do: Replace reed valve → clean discharge muffler (remove metal particles and carbonized oil) → test refrigerant acidity (if acidic, replace all refrigerant + swap dryer) → after reassembly, observe high-side pressure drop immediately after shutdown (backflow suspected if > 0.5 MPa drop within 1 minute)

Moisture or acid in refrigerant corrodes reed valve surface

Check: Check refrigerant pH with litmus paper or dedicated acid test kit — acid reaction confirms contamination. If filter-dryer surface is cooler than ambient, it is saturated

What to do: Recover all refrigerant → replace filter dryer → vacuum to below 500 μmHg for ≥30 minutes → charge new refrigerant to spec → recheck acidity after 24 hours of operation

Liquid slug or overcharge causes instantaneous overpressure on reed valve → plastic deformation

Check: Measure suction superheat: normal 5–10°C; if < 3°C, liquid back is likely. Verify charge amount (scale charging): check if overcharged > 10% above spec

What to do: If overcharged, recover excess refrigerant → readjust TXV (target superheat 5–8°C) → confirm crankcase heater is permanently ON → replace reed valve and recharge

Field tip

If high-side pressure equalizes with low-side within 1 minute of compressor shutdown, suspect discharge reed valve backflow first. If pressure ratio is low without scoring, the problem is the valve.

All 565 cases work offline in R-Pro, with error codes for 62 brands and P-T data for 108 refrigerants.

Open R-Pro →

Related cases